Has he discussed this with his pdoc? I think if he hasn't, you could tell him to do so; for both of your well-beings.
Also, try not to stay in that kind of situtation if he starts becoming abusive. Set the rule down ahead of time, if he begins to hurt you, then he should know you're out of there, until he can better himself. (because if you allow him to continue, and he likes himself off of it, then what reason, or incentive to have to seek help for his issues?).

Sounds like he is having undesirable side effects from this med. There are many more out there on the market. Is there a way to suggest to him to seek out his pdoc and look into the other options?
*hugs* I mean this all in a nice way, and i hope it didn't come out roughly.